Adjustable system feeding an electric motor through a resistance of a variable value



D 10, 19 JEAN-CLAUDE LAGIER 3,416,059

I ADJUSTABLE SYSTEM FEEDING AN ELECTRIC MOTOR THROUGH A RESISTANCE OF A VARIABLE VALUE Filed Feb. 16. 1966 INVENTOR JEAN 6; nova L n Eg ATTORNEY United States Patent 3,416,059 ADJUSTABLE SYSTEM FEEDING AN ELECTRIC MOTOR THROUGH A RESISTANCE OF A VARI- ABLE VALUE Jean-Claude Lagier, Onex-Geneva, Switzerland, assignor to Mefina S.A., Fribourg, Switzerland, a corporation of Switzerland Filed Feb. 16, 1966, Ser. No. 527,693 Claims priority, application Switzerland, Mar. 19, 1965, 3,884/ 65 1 Claim. (Cl. 318-348) ABSTRACT OF THE DISCLOSURE An adjustable system for feeding alternating current into an electric motor including a pair of variable resistances one of which is in series with a diode while the diode is shunted by the other resistance. A control member initially successively short-circuits the first resistance to provide a lower range of powers and thereafter successively short-circuits the second resistance to provide a higher range of powers.

The present invention has for its object an adjusting system incorporating a variable resistance for feeding alternating current into an electric motor driving a sewing machine for instance. Such systems include generally at least one adjustable resistance inserted in series with the motor, a control member adapted to insert in the circuit feeding the motor one, several or none of the elementary resistances forming sai-d adjustable resistance or resistances and at least one diode adapted to be inserted in the feeding circuit so as to cut out one of alternations of the motor-feeding alternating current and to reduce the speed of the motor while the heat evolved in the elementary resistances in the circuit is reduced.

The system according to the invention diflfers from the known systems of the type disclosed hereinabove through the fact that the diode is inserted in series with a number of elementary resistances and is shunted by the remaining elementary resistances while the control member ensures through a successive short-circuiting of the first mentioned elementary resistances an adjustment within a first lower range of powers and then through a successive short-circuiting in succession of the other elementary resistances an adjustment within a second higher range of powers.

The single figure of the accompanying drawing illustrates by way of example in a diagrammatic manner a preferred embodiment of said improved system.

As illustrated, the adjusting system provided with a variable resistance R +R for an electric motor M adapted more particularly for the driving of a sewing machine includes a control member 0. Said control member provides for the short circuiting in a gradual manner of the elementary resistances r r r inserted in series with the motor M and forming the resistance R This being done, said control member 0 cuts oif the resistance R and inserts the resistance R in the circuit and thereafter short-circuits the elementary resistances 'r and r inserted in series with the motor M and forming the resistance R As a matter of fact and as illustrated, the series 3,416,059 Patented Dec. 10, 1968 hce of elementary resistances forming the resistance R are connected each with a contact-piece C C or C Similarly the elementary resistances r' r' forming the resistance R are connected with the corresponding contact pieces C' C' In the example illustrated, the control member 0 is assumed to form a rotary member carrying a sectorshaped extension S engaging in succession the cont-actpieces C to C and then the contact-pieces C' to C when the control member 0 is caused to rock round its axis. The alternating current circuit feeding the motor M includes furthermore a diode D inserted in series with the resistance R and an element E shunting the diode and protecting it. Said element E may be constituted by a resistance. In the wiring diagram illustrated, the elementary resistances r r r are inserted in series with the diode D whereas the elementary resistances r',, r are in shunt relationship with the diode D.

The operation of said embodiment is as follows: The terminals V being connected with the alternating current mains, no current passes through the motor M as long as the control member 0 lies in the position illustrated so that the motor M remains stationary. As soon as the sector S reaches the contact piece 0,, a weak current passes through the resistance R, as a whole and through the diode D into the motor M. Thus, the motor M is fed by one half alternation of the current and its power increases upon shifting of the control member 0 from the contactpiece C towards the contact-piece C, connected directly with the diode D. When the control member 0 is shifted from the contact-piece C towards the further contactpiece C, the diode D is cut off and the motor M is fed by both alternations of the current through the resistance R and operates consequently under higher power conditions. Said power may be still further increased by shifting the control member 0 from the contact-piece C' forwardly towards the contact-piece C which cuts out the resistance R The embodiment disclosed allows thus obtaining a gradual speed adjustment for a universal motor with a reduced heating of the resistances inserted in the circuit since, for a fraction of the adjusting range, only one halfalternation of the feed current is used.

The wiring diagram referred to is of an extremely simple and inexpensive execution since the single elec tronic element incorporated therewith is constituted by a diode, in contradistinction with certain prior systems which resort to several electronic elements such as controlled diodes for instance.

In the system illustrated, it has been assumed that the control member 0 is a rotary member; obviously such a control member may be replaced by a member controlled by a push-button or a rocking lever adapted to shortcircuit in succession through the different contact-pieces C C the different elementary resistances connected with the latter.

I claim:

1. In combination with a universal motor, a system feeding current to said motor and including a supply of alternating current, a circuit including two sections adapted to be inserted selectively between the supply and the motor to feed the latter, a resistance inserted in each circuit section and each including a number of elementary resistances in series, a rectifying diode inserted in series with one of the resistances, a control member and a num- References Cited ber of contact-pieces connected with the ends of the UNITED STATES PATENTS different elementary resistances and adapted to be operated in succession by the control member to execute the follow- 3,180,999 4/1965 PY ing successive operations: closing the circuit to the motor 5 3,310,722 3/1967 D1611 318 349 X through all the elementary resistances of said one resistance and through the diode, cutting out said elementary ORIS RADER Pnmm'y Examiner resistances in succession, closing the circuit to the motor D. SIMMONS, Assistant Examiner. through all the elementary resistances of the other resistance and cutting out in succession said last-mentioned 10 US C .R- resistances. 318-249, 514, 509. 

